Searchlights for use in fog and mist



May 11, 1965 PAUL EULER DE SALLES COELHO 3,183,347

SEARCHLIGHTS FOR USE IN FOG AND MIST Filed Aug. 17, 1962 2 Sheets-Sheet 1 IIGJ.

PAUL Euuaa 0e SELL-ES COELHO ATTORNEYS y 1965 PAUL EULER DE SALLES CO ELHO 3,183,347

SEARCHLIGHTS FOR USE IN FOG AND MIST Filed Aug. 17, 1962 2 Sheets-Sheet 2 W "mil 9 Wu 0 l O I INV ENT OR PAUL Euuza DE Snwas Cos LHO ATTORNEYS United States Patent 3,183,347 SEARCHLIGHTS FOR USE IN FOG AND MIST Paul Euler de Salles Coelho, Rua Sao Jose 907 and., Rio de Janeiro, Brazil Filed Aug. 17, 1962, Ser. No. 217,675 Claims priority, application Brazil, Feb. 23, 1962, 136,710 2 Claims. (Cl. 240-4623) Searchlights are well-known and widely used in civil and military night reconnaissance and identification, owing to their powerful beam of light. However, such searchlights are of little use, when it is attempted to use them through fog, mist, clouds, or the like. It is because, in these atmospheric states, the visibility which could be obtained decreases due to two factors:

(a) The penetration of the luminous flux lessens by scattering when these atmospheric conditions exist, and consequently, the illumination of distant objects decreases.

(b) The rays of light, being reflected on the droplets by the atmospheric condition, create a luminous foreground which prevents or makes it diflicult to perceive objects situated at further, and thus, less illuminated points.

The improvement covered by the present invention consists in the introduction of a device which permits the lessening of the effect mentioned in (b), which will permit a considerable improvement in visibility.

The objective is to diminish the detrimental effect on visibility of the reflection of the luminous rays on the particles forming fog, mist, clouds and the like, situated between the observer and the target.

This will be obtained by means of a selection of the luminous flux emitted and the luminous flux received, as will be described hereinbelow.

For this purpose, the invention provides a device for producing an emission for a certain short time during which the observer does not receive any visual impression. After the emission, there follows a short space of time without emission and which is referred to as AT, during which the observer doe-s not receive any visual impression of the flux emitted. During this short space of time AT the whole of the luminous flux emitted will move at the speed of light and will cover a distance L, before it will be possible to see the reflected rays.

The result of this is that the first visual impressions to be received will be those derived from the reflection of the rays belonging to the luminous flux in particles of the atmospheric phenomenon located at the distance L/ 2 from the device. Inasmuch as this is the minimum distance which the part of the luminous flux nearest to the device, when the emission is suspended, should attain in order, upon returning after the reflection, to complete the distance L relating to the time AT after which the luminous impressions are admitted. Therefore, when the emission is interrupted, the luminous rays which reflect up to the distance L/ 2 will return to the device but will not be perceived inasmuch as there will not have elapsed the time AT after which the luminous perceptions begin. This elimination of perception of the rays reflected between the device and the distance already mentioned will considerably improve the observation of the objects situated at the distances greater than L/ 2.

The invention will herein be described as an example with the aid of the attached drawings, in which:

FIGURE 1 is a schematic representation of the present invention; and

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FIGURES 2 to 7 represent in a plan view, various positions of the movable disc which forms part of the invention.

The invention includes the searchlight 1, FIGURE 1, which is divided into two parts between which rotates a certain portion of a movable disc 5 which has apertures that operate as movable apertures. It also has a motor 21 the shaft 7 of which is coupled to disc 5, which rotates jointly therewith. A sighting member 8 is also divided into two parts in similar manner as the searchlight 1 and the axis of which is perpendicular to the plane of the disc. A certain portion of movable disc 5 passes between the two parts of sighting member 8.

In searchlight 1 there is located at 2 the luminous source for the searchlight disposed on the main axis thereof, a condenser lens 3, a fixed aperture 4 and an objective lens 6.

The luminous rays emitted by the source 2 reach the condenser lens 3 and proceed to form a real luminous image from the source over a fixed aperture 4, placed at a suitable distance. This real image, outlined by the fixed aperture 4, is situated beside the back focus of the objective lens 6. When the movable disc 5 is in such a position that there is a coincidence between the fixed aperture 4 and one of the movable apertures of the disc 5, the luminous rays will reach the objective lens 6 from which they will emanate forming a small opening beam of light. After reflection on the target, the luminous rays will reach the observers retina through the sighting member 8, when the fixed aperture 9 of the sighting member 8 coincides with one of the movable apertures for said sighting member also located on the movable disc 5.

The sighting member 8 has no lens and its purpose is merely to aid the observer at the ocular 10 in order to keep his eye or eyes in such a position so as to avoid re ceiving luminous impressions before there is coincidence between the aperture 9 of the sighting member 8 with the eventual movable aperture for the sighting member located on the movable disc 5.

However, if it should be considered convenient to provide a visual observation with amplification, a lens sys tem can be provided in sighting member 8. A complete cycle comprising three phases: emission, interval and visual reception of the luminous rays will now be described.

In FIGURE 2 the following elements 11 and 12 represent two of the movable apertures for the searchlight 1, while 13 and 14 represent two of the movable apertures for sighting member 8; 9 represents the fixed apertures of the sighting member 8 whereas 4 represents the fixed apertures of the searchlight 1.

The rotation shaft of the disc 5 is represented at 7. Let it be assumed that the direction of disc 5 is clockwise. In FIGURE 2, there is represented the start of a cycle, that is to say, the movable aperture 11 is tangential to the projection of the fixed aperture 4 and the emission of light is therefore about to start due to the direciton of rotation of the movable disc 5. At this same moment, the movable aperture 13 of the sighting member 8 is tangent to the fixed aperture 9 of sighting member 8; thus no further luminous impressions will be transmitted at this instant due to the direction of the movable disc 5. The movable disc 5 rotating at a slight angle, moves to the position represented in FIGURE 3 where it is observed that the movable aperture 11 is fully coincident to the 3 fixed aperture 14 of searchlight 1 and consequently there is emission of light.

It is also observed that movable aperture 13 of sighting member 8 has moved away from fixed aperture 9 thereof, and that no luminous impression is being receievd at that moment by an observer through ocular 10 of sighting member 8.

The disc continuing to rotate clockwise, there can be seen, in FIGURE 4, one or more stages of the cycle. At this moment, the movable aperture 11 of searchlight 1 is tangential to the fixed aperture 4 of searchlight 1, the emission of light thus ceasing. It can also be observed in FIGURE 4 that the movable aperture 13 of sighting member 8 has moved still further away from the fixed aperture 9 thereof. It will also be seen that the movable aperture 14 for sighting member 8 approaches the fixed aperture 9 thereof, but that it is sti necessary for the disc 5 to move a certain angle for its coincidence to start, with the result beginning the luminous perceptions. In order that such start of the coincidence might take place, there will elapse a space of time AT which, as already explained above, will result in only luminous impressions being received which are derived from a distance equal to or greater than L/ 2, where L represents the distance covered, at the speed of light, by the part of the luminous flux which has not been reflected.

FIGURE 5 represents the start of the part of the cycle intended for visual perception. As can be seen the movable aperture 14 is tangential to the fixed aperture 9 of sighting member 8 for the start of visual receptions. It may be seen in FIGURE 5 that at this moment there is no coincidence of the fixed and movable apertures 4 and 11 and 12, respectively of searchlight 1, and there is therefore no luminous emission.

In FIGURE 6 there has been represented another position of the movable disc 5 in which there is full coincidence of the fixed aperture 9 and the movable one 14 of sighting member 8 in the same figure, there can be observed that in this interval there is no luminous emission. The movable disc 5 continuing to rotate, after a certain time, it will have reached the position represented in FIGURE 7 which represents the end of the cycle which has been heretofore explained and the beginning of a subsequent cycle. In fact, the movable aperture 12 of serachlight 1 is now occupying the same position which the movable aperture 11 thereof occupied in FIG- URE 2, and also, the movable aperture 14 of sighting member 8 is occupying the same position as the movable aperture 13 in FIGURE 2.

In short, in the movable disc 5 the apertures for the searchlight 1 and sighting member 8 are symmetrically arranged in relation to their rotation axis and occupy posiitons which permit in cooperation with the respective fixed apertures and for each cycle: 1st, that there is no visual reception when there is emmisison; 2nd, that there is a period without emission and without luminous reception; and 3rd, that there is a visual reception period during which there is no luminous emission.

Since 11 is the number of movable apertures for searchlight 1, n will also be the number of movable apertures for sighting member 8. For a complete rotation of the movable disc 5 there will be n complete cycles. If the motor is capable of making the disc make N rotations per second, there will be, in each second nXN complete cycles. The number of cycles is normally much greater than 12 cycles per second and therefore persistent images in the observers retina will be formed.

For each apparatus and also depending on the intensity of the atmospheric condition, there will be a maximum distace of visibility possible, which will depend upon the distance between the target and the distance L/ 2 up to which the direct reflections of the luminous rays emitted will not be seen. On the other hand, the distance L/2 varies in accordance with the time AT during which there is neither emission nor luminous reception. The motor 21 which makes the movable disc 5 rotate should therefore have preferably a variable speed which will make it possible by the variation of the AT and, consequently of L/2 to verify the point where best visibility is obtained, the speed of the motor being set thereon.

Another way of promoting the time variation AT, by means of a constant speed motor, would be to provide the possibility of very small displacements for sighting member 8 concentrically with the shaft of the shaft of the disc, which would permit the reduciton, at will, of the distance shown in FIGURE 4 and separating the movable diaphragm 14 of disc 5 from the diaphragm 9 of sighting member 8 with a corresponding reduction of the time At, necessary for coincidence purposes: the sighting member 8 should then be fixed at the point of best visibility.

At present there is nothing to improve visibilty obtained with the use of searchlights through mist, fog, clouds, and the like. There is used only the devices in which an observer withdraws sideways from the searchlights, striving for such a position as will permit him to avoid partly the direct reflection of the luminous rays which are reflected in the droplets of atmospheric phenomena, which is obviously a precarious and not always possible solution. With the special device which is the object of the present invention, it is possible without having to move away from the apparatus, to avoid, to a great extent, the undesirable effects of the luminous reflection from the rays on the atmospheric particles situated between the observer and the target. It should therefore be very useful in air, sea and land transport. In short, in all uses where, by means of searchlights, it is endeavored to obtain better visibility through the already mentioned atmospheric conditions.

The subject of the present invention, described herein merely as an example, in practice naturally comprises all the modifications covered by the scope of the claims which follow.

What is claimed is:

1. An apparatus for improving the illumination of an object during adverse weather conditions comprising searchlight means for emitting and projecting a beam of light along an emitting path toward said object, disk means having apertures therein, said disk means having a portion including said apertures disposed within the emitting path of said beam of light, and means operatively connected to said disk means for rotating said disk means so as to cause said beam of light to be intermittently projected by said apertures toward said object, a sighting device being disposed adjacent and parallel to said searchlight means, said disk means including said apertures being disposed within the line of sight of said sighting device, said apertures being spaced at intervals and defining first and second concentric circles in said disk means, said first concentric circle of apertures intersecting said emitting path, said second concentric circle of apertures intersecting the line of sight of said sighting device, the apertures of said first and second concentric circles being positioned on said disk means so that when light is projected through an aperture of said first concentric circle, said disk means blocks the line of sight of said sighting device.

2. An apparatus for improving the illumination of an object during adverse weather conditions comprising searchlight means for emitting and projecting a light along an emitting path toward said object, disk means having apertures disposed therein at predetermnied angular positions and in first and second concentric circles on said disk means, and means operatively connected to said disk means for rotating said disk means so that the apertures of said first concentric circle intersect said light-emitting path to cause said beam of light to be intermittently proected by said apertures toward said object to enable the light beam engaging droplets of moisture to be dispersed before being perceived, said first and second concentric circles and said disk means having the same axis of rotation, sighting means disposed parallel with and spaced from said Searchlight means, said sighting means observing on a line of sight which intersects the apertures of said second concentric circle, and said apertures of said first and second concentric circles being positioned so that the sequence of events during rotation of said disk means is emitting light with non-observation, non-emission of light and non-observation, and observation with non-emission of light.

References Cited by the Examiner UNITED STATES PATENTS NORTON ANSHER, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,183,347 May 11, 1965 Paulo Euler de Salles Coelho It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

In the grant, lines 1 and 12, and in the heading to the printed specification, line 3, for "Paul", each occurrence, read Paulo in the heading to the drawings, Sheets 1 and 2, line 1, for "PAUL", each occurrence, read PAULO in the drawings, Sheets 1 and 2, lower righthand corner, for "Paul", each occurrence, read Paulo Signed and sealed this 8th day of February 1966.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

1. AN APPARATUS FOR IMPROVING THE ILLUMINATION OF AN OBJECT DURING ADVERSE WEATHER CONDITIONS COMPRISING SEARCHLIGHT MEANS FOR EMITTING AND PROJECTING A BEAM OF LIGHT ALONG AN EMITTING PATH TOWARD SAID OBJECT, DISK MEANS HAVING APERTURES THEREIN, SAID DISK MEANS HAVING A PORTION INCLUDING SAID APERTURES, DISPOSED WITHIN THE EMITTING PATH OF SAID BEAM OF LIGHT, AND MEANS OPERATIVELY CONNECTED TO SAID DISK MEANS FOR ROTATING SAID DISK MEANS SO AS TO CAUSE SAID BEAMS OF LIGHT TO BE INTERMITTENTLY PROJECTED BY SAID APERTURES TOWARD SAID OBJECT A SIGHTING DEVICE BEING DISPOSED ADJACENT AND PARALLEL TO SAID SEARCHING MEANS, SAID DISK MEANS INCLUDING SAID APERTURES BEING DISPOSED WITHIN THE LINE OF SIGHT OF SAID SIGHTING DEVICE, SAID APERTURES BEING SPACED AT INTERVALS AND DEFINING FIRST AND SECOND CONCENTRIC CIRCLES IN SAID DISK MEANS, SAID FIRST CONCENTRIC CIRCLE OF APERTURES INTERSECTING SAID EMITTING PATH, SAID SECOND CONCENTRIC CIRCLE OF APERTURES INTERSECTING THE LINE OF SIGHT OF SAID SIGHTING DEVICE, THE APERTURES OF SAID FIRST AND SECOND CONCENTRIC CIRCLES BEING POSITIONED ON SAID DISK MEANS SO THAT WHEN LIGHT IS PROJECTED THROUGH AN APERTURE OF SAID FIRST CONCENTRIC CIRCLE, SAID DISK MEANS BLOCKS THE LINE OF SIGHT OF SAID SIGHTING DEVICE. 